Puerto Rico Weather

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST WED AUG 24 2016

.SYNOPSIS...At upper levels...Weak high pressure will accompany
the strong tropical wave as it crosses the area today and
Thursday. Then northerly flow will persist until Sunday when the
effects of a trough moving toward the area will be felt. The
trough will cross through the U.s. Virgin Islands Monday and
followed by a modest ridge that will cause flow to strengthen
considerably late next week.

At mid levels...The mid level troughing accompanying the tropical
wave will be followed by very weak high pressure that intervenes
between the Caribbean and the potential Hurricane Gaston over the
weekend. During the up coming week, high pressure builds north of
the forecast area until a trough moves west over the area on
Friday of next week.

At lower levels...A strong tropical wave has only traces of
circulation indicated and will pass over the area today. Then
gradients will remain relatively weak over Puerto Rico and the
U.S. Virgin Islands as Gaston intervenes between high pressure
just west of the Azore islands and the local area. High pressure
and moderate trade wind flow returns next week and continue
through the end of that week.

&&

.DISCUSSION...Scattered showers and isolated thunderstorms
affected Puerto Rico north of the Cordillera Central and the
northern U.S. Virgin Islands overnight. Showers have become a
little more numerous in the pre-dawn hours and rain is expected
across the Northern tier of Puerto Rico this morning, with showers
continuing into the afternoon as the wind switches from northeast
to southeast rather abruptly later this morning.

Very vigorous displays of lightning have been seen north and
northeast of Guadeloupe and this area is slowly moving west
northwest. Isolated lighting strikes have occurred in the forecast
area and midway between saint Croix and Saint Kitts. Thunderstorm
activity will increase area-wide today.

Models appear to be in good agreement with the timing and
intensity of the rainfall and flash flooding potential
continues--especially for the eastern half of Puerto Rico this
morning and early afternoon. Drying was seen late this afternoon
over the southeast half of the forecast area, but another influx
of moisture is seen pushing into the area early Thursday morning
with showers likely again Thursday morning in the southeast half
of Puerto Rico.

The GFS continues with deep moisture through at least Sunday so
that fair weather is not expected in the area for almost the next
7 days. The upper level low northeast of the forecast area moves
closer during the week, but then dissipates and high pressure
replaces it north of the forecast area. Nevertheless the upper
level trough transiting the Caribbean on Monday should increase
the chance of showers and thunderstorms in the local area.

&&

.AVIATION...Strong tropical wave across the eastern Caribbean
will continue to move west-northwest impacting all terminals.
SHRA/TSRA associated to the wave will result in MVFR to IFR conds.
Showers and thunderstorms already affecting TNCM/TKPK are
expected to become more frequent through the early morning hours
across the northern/eastern terminals of PR and the USVI,
spreading across the rest of the terminals by 16z. Low level winds
expected to continue ENE at 7-15 knots thru 12z...veering ESE
afterwards. Gusty winds between 25-35 kts possible with TSRA.

&&

.MARINE...Winds have been confined to the area northeast of a
northwest-southeast line through the low and apex of the wave.
Hence it appears that high seas and strong winds will be mostly
confined to the northeast corner of the forecast area. Winds of 18
knots sustained have been noted at buoy 41043. Recent gusts have
reached 25 knots, but 31 knots was noted around 24/01z. Although
the low/apex of the wave is very close, current forecasts are
showing these winds to remain north of Puerto Rico and the U.S.
Virgin Islands at this time.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 77 87 76 / 80 80 70 40
STT 83 78 84 79 / 80 80 70 40

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST FRI AUG 26 2016

.SYNOPSIS...TUTT low now located across the central Atlantic, will
shift west-southwestward into the Greater Antilles while weakening.
As this feature moves away from the local islands early next week,
an upper level ridge will build across the forecast area. A moist
east southeast wind flow will continue to prevail today, promoting
shower and thunder activity across the area.

&&

.DISCUSSION...Partly to variably cloudy skies prevailed overnight and
early this morning across the local islands. Showers and a few isolated
thunderstorms were observed across the Caribbean waters with a few of
them affecting the local islands. Coastal temperatures were in the
upper 70s to low 80s with southeasterly winds at 10 mph or less.

Approaching TUTT will meander northeast of the forecast area through
Sunday. Although TUTT location will tend to favor a convergent
pattern across the area, the east southeast wind flow will continue
to advect enough low level moisture to result in showers across S/SE
PR and Saint Croix this morning, followed by afternoon convection
over and northwest of the Cordillera Central. A similar weather
pattern is expected Sat-Sun, but coverage should decrease as low
level moisture decreases. This ESE wind flow will also promote
warm temperatures along the northern slope of Puerto Rico.

As the TUTT low relocates to our west on Monday, a ridge pattern
aloft will build across the area from the east northeast. Under
building upper level ridge, moderate easterly winds and precipitable
water near or below normal values, a seasonable weather pattern
will prevail Mon-Thu with a few passing showers across windward
areas in the morning and evening hours and locally induced
afternoon showers and thunderstorms over and west of the
Cordillera Central.

&&

.AVIATION...Showers will affect TIST/TISX/TJPS/TJSJ through the
morning hours. SHRA are expected to increase in frequency aft 2610z
over land, then afternoon convection may produce mountain
obscuration across the Cordillera Central. In addition, between
26/17-26/22z...periods of MVFR conditions with mountain obscurations
can be expected over TJMZ and TJBQ. Low level winds will be mainly
southeast at 10 to 15 kts and locally higher inland around SHRA/TSRA.

&&

.MARINE...Seas of 3-5 feet expected during the next few days. Small
easterly swell by TC Gaston is expected to reach the coastal waters
of all islands on Saturday. No small craft advisories are anticipated
over the next 5-7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 80 91 80 / 30 30 30 20
STT 90 80 90 80 / 50 30 30 40

Area Forecast Discussion
National Weather Service San Juan PR
550 AM AST SUN AUG 28 2016

.SYNOPSIS...
The influence of Hurricane Gaston, well northeast of the region
across the Central atlantic, and a broad area of low pressure
near the Florida Straits, will continue to induce a moist
southeast wind flow across the region through at least Monday. A
TUTT Low to the Northeast of the area will retrogress westward to
meander across the region at least until Tuesday as an Upper level
ridge builds over the region by midweek.

&&

.DISCUSSION...
The proximity of a TUTT Low produced showers across the local
waters overnight, some of these showers, though they were brief,
moved inland across the windward sections of PR and the U.S.
Virgin Islands. In addition, the diffluence aloft induced the
formation of thunderstorms in the far Southwest corner, between
the Mona Passage and the local Caribbean Offshore waters.

The combination of the TUTT low, an induce surface trough and the
available low level moisture will continue to enhance shower
activity across the surrounding waters and some of these showers
are going to reach the windward sections of PR and the U.S. Virgin
Islands from time to time during the morning hours. Then, another
round of afternoon convection is expected along the Cordillera
Central and the western sections of Puerto Rico, but also, some
of these showers could affect the metropolitan area of San Juan.

As the TUTT low moves away from the region on Tuesday, a ridge
pattern aloft will build from the east northeast, over the
Northeast Caribbean. In addition, the surface winds are expected
to become from the east and precipitable water will drop near or
below normal by midweek. This pattern will result in limited
shower and thunderstorm activity across the local islands.

&&

.AVIATION...
Mostly VFR conditions expected over most of the local flying
area. However vicinity showers are possible until 28/14Z across
the Leeward and USVI taf sites. Isolated tstms will affect the
vicinity of TJSJ/TJBQ and TJMZ after 28/17 and through 28/23z with
mountain top obscuration across the Cordillera Central of PR. Low
level winds will be mainly east at 10 knots overnight increasing
to 10 to 15 knots after 28/13Z.

&&

.MARINE...A small, but long ENE swell, generated by Tropical
Cyclone Gaston will continue to affect the local Atlantic waters
and Anegada through at least late tonight, followed by arrival of
another small but long NE swell by late Tuesday. Although this
swells, seas are expected below 6 feet and winds around 15 knots.
At this moment, marine weather conditions are expected below small
craft criteria. However, isolated thunderstorms with areas of
locally heavy rainfall and dangerous lightning will remain
possible across the regional waters as the TUTT Low moves across
the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 91 80 / 30 20 30 10
STT 86 80 87 81 / 30 30 30 10

&&

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST TUE AUG 30 2016

.SYNOPSIS...Upper level ridge will dominates the local region
through most of the week. An active tropical wave will approach
the northeast Caribbean by the weekend.

&&

.DISCUSSION...Some light passing showers were noted across the
local waters. No showers were observed over land areas. As the
TUTT low moves away from the local islands, a ridge pattern aloft
will build from the east northeast. Under building upper level
ridge, moderate easterly winds and precipitable water near or
below normal values, a seasonable weather pattern will prevail
through at least Thursday with a few locally induced afternoon
showers and thunderstorms over and west of the Cordillera Central
as well as warm to hot temperatures along the northern slopes of
Puerto Rico.

An active tropical wave is expected to approach the northeast
Caribbean during the weekend. An increase in shower and
thunderstorms activity is expected...mainly by early next week. At
this time...it is too early to know exactly how active this wave
will be across the region. Stay tuned.

&&

.AVIATION...VFR conditions expected across the local flying area
until 30/15Z. After 30/17Z, SHRA/TSRA expected to develop across
western and interior Puerto Rico, affecting the vicinity of TJMZ
through 30/22Z with mountain top obscuration. Low level winds will
be from the ESE at 15-25 knots.

&&

.MARINE...Seas up to 5 feet and winds up to 20 knots are expected.
Small craft should exercise caution across the Atlantic waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 92 81 92 80 / 20 20 20 20
STT 90 80 91 80 / 20 20 20 20

Area Forecast Discussion
National Weather Service San Juan PR
600 AM AST THU SEP 1 2016

.SYNOPSIS...
A mid to upper level ridge will continue to build over the region
today through the weekend. A weak tropical wave is expected to
move across the region late tonight and Friday. A dry air mass
with suspended dust particles is expected through the weekend.
A tropical wave is expected to reach the local islands Sunday or
Monday.

&&

.DISCUSSION...
The Doppler Radar detected limited shower activity overland during
the overnight hours. However a line of showers moved along the
north coastline of Puerto Rico around midnight. For today, under
the prevailing mid to upper level ridge, expect a strong cap
inversion across the region, which should limit afternoon
convection across the islands. However, trade wind showers are
expected from time to time across the islands without any
significant rainfall amounts. Late this afternoon and into
Friday, shower should increase in coverage as the moisture of a
weak tropical wave reach the islands. Therefore, showers and
thunderstorms should increase somewhat on Friday.

A Saharan Air layer is expected to reach the CWA Saturday through
Sunday, to result in hazy skies. But the combination of daytime
heating and local effects could produce some localize afternoon
convection each day across the interior and west PR. A strong
tropical wave is expected to reach the local islands on Sunday or
Monday. If the model guidance are correct, showers and
thunderstorms should increase in coverage and intensity. In
additions, squally weather is possible with this system.

&&

.AVIATION...
Mostly VFR conditions expected across all terminals through the
forecast period. However, shra/-tsra over western PR impacting
mainly TJMZ still possible thru 01/17z-22z. Low level winds will
continue East at 15-30 kts below FL250.

&&

.MARINE...
A slight increase in the easterly trade winds will continue to
produce choppy seas between 4 and 6 feet across most of the local
waters. As a result, small craft operators should exercise caution
across most of the local waters, due to seas between 4 and 6 feet
and winds up to 20 knots.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 80 89 81 / 20 40 40 30
STT 91 83 89 83 / 20 40 40 30

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
510 AM AST SAT SEP 3 2016

.SYNOPSIS...Mid level ridge across the forecast area is expected
to slowly erode during the next few days. A surface high pressure
north of the area will continue to promote easterly winds through
next week with the local pressure gradient tightening between Sun-
Mon. As a result, winds are expected to increase across the
forecast area. A mainly fair weather pattern will continue to
prevail through the next tropical wave passage which is expected
late Sunday into Monday.

&&

.DISCUSSION...Partly cloudy skies prevailed across the local
islands overnight and early this morning. Some passing showers
were noted over the local waters as well as the USVI and NE PR.
Low temperatures ranged from the low to mid 70s in the mountains
to the upper 70s to low 80s elsewhere.

Under the eroding mid level ridge, moderate to locally fresh
easterly winds and near to below normal precipitable water, a
mainly fair weather pattern will prevail through Sunday with
locally induced afternoon showers and thunderstorms across west
Puerto Rico each day.

The local weather pattern is expected to change late Sunday and
into Monday as a tropical wave moves across the eastern Caribbean.
Based on the latest NHC Tropical Weather Outlook, this wave at
2am AST was located about 800 miles east of the Lesser Antilles
and environmental conditions are only marginally conducive to
development. Development, if any, should be slow to occur. The
formation chance through the next 48 hours is low, 20 percent.
And in fact, latest guidance suggested bulk of moisture remaining
over the Caribbean waters and south of PR and the USVI.

However, low level moisture will increase across the area late
Sunday and into Monday with lingering moisture prevailing through
Tuesday. Winds are also expected to increase with the tropical
wave passage. As a result, periods of squally weather could be
expected late Sunday through early Tuesday, and focused across
the east and south sections of forecast area.

&&

.AVIATION...Mostly VFR conditions expected with vicinity SHRA
possible across the USVI, Leeward Islands and Eastern PR terminals.
After 03/17Z, SHRA/TSRA expected to develop across southwestern
Puerto Rico, affecting the vicinity of TJMZ and TJPS through 03/22Z
with mountain top obscuration. In addition, Sfc winds expected
from the E-ENE below 10 kt til 03/13z, increasing to 10-15 kts
with higher gusts after 03/13Z.

&&

.MARINE...Marine conditions will deteriorate between Sunday and
Monday as winds and seas increase due to a tropical wave. Although
the shower activity associated with the wave will remain mostly
over the Caribbean Waters, the seas will build to around 5-7 feet
across most of the waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 80 89 79 / 20 20 20 50
STT 91 81 91 80 / 20 20 20 50